[Qemu-devel] [PATCH 2/3] pc-bios/s390-ccw/net: Add support for pxelinux-style config files

[Thomas Huth <thuth@redhat.com>]

Since it is quite cumbersome to manually create a combined kernel with
initrd image for network booting, we now support loading via pxelinux
configuration files, too. In these files, the kernel, initrd and command
line parameters can be specified seperately, and the firmware then takes
care of glueing everything together in memory after the files have been
downloaded. See this URL for details about the config file layout:
https://www.syslinux.org/wiki/index.php?title=PXELINUX

The user can either specify a config file directly as bootfile via DHCP
(but in this case, the file has to start either with "default" or a "#"
comment so we can distinguish it from binary kernels), or a folder (i.e.
the bootfile name must end with "/") where the firmware should look for
the typical pxelinux.cfg file names, e.g. based on MAC or IP address.
We also support the pxelinux.cfg DHCP options 209 and 210 from RFC 5071.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 pc-bios/s390-ccw/netboot.mak |  7 ++--
 pc-bios/s390-ccw/netmain.c   | 79 +++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 82 insertions(+), 4 deletions(-)

diff --git a/pc-bios/s390-ccw/netboot.mak b/pc-bios/s390-ccw/netboot.mak
index a73be36..8af0cfd 100644
--- a/pc-bios/s390-ccw/netboot.mak
+++ b/pc-bios/s390-ccw/netboot.mak
@@ -25,8 +25,9 @@ CTYPE_OBJS = isdigit.o isxdigit.o toupper.o
 %.o : $(SLOF_DIR)/lib/libc/ctype/%.c
 	$(call quiet-command,$(CC) $(LIBC_CFLAGS) -c -o $@ $<,"CC","$(TARGET_DIR)$@")
 
-STRING_OBJS = strcat.o strchr.o strcmp.o strcpy.o strlen.o strncmp.o strncpy.o \
-	      strstr.o memset.o memcpy.o memmove.o memcmp.o
+STRING_OBJS = strcat.o strchr.o strrchr.o strcpy.o strlen.o strncpy.o \
+	      strcmp.o strncmp.o strcasecmp.o strncasecmp.o strstr.o \
+	      memset.o memcpy.o memmove.o memcmp.o
 %.o : $(SLOF_DIR)/lib/libc/string/%.c
 	$(call quiet-command,$(CC) $(LIBC_CFLAGS) -c -o $@ $<,"CC","$(TARGET_DIR)$@")
 
@@ -50,7 +51,7 @@ libc.a: $(LIBCOBJS)
 # libnet files:
 
 LIBNETOBJS := args.o dhcp.o dns.o icmpv6.o ipv6.o tcp.o udp.o bootp.o \
-	      dhcpv6.o ethernet.o ipv4.o ndp.o tftp.o
+	      dhcpv6.o ethernet.o ipv4.o ndp.o tftp.o pxelinux.o
 LIBNETCFLAGS := $(QEMU_CFLAGS) -DDHCPARCH=0x1F $(LIBC_INC) $(LIBNET_INC)
 
 %.o : $(SLOF_DIR)/lib/libnet/%.c
diff --git a/pc-bios/s390-ccw/netmain.c b/pc-bios/s390-ccw/netmain.c
index 7533cf7..e84bb2b 100644
--- a/pc-bios/s390-ccw/netmain.c
+++ b/pc-bios/s390-ccw/netmain.c
@@ -30,6 +30,7 @@
 #include <ipv6.h>
 #include <dns.h>
 #include <time.h>
+#include <pxelinux.h>
 
 #include "s390-ccw.h"
 #include "virtio.h"
@@ -41,12 +42,14 @@ extern char _start[];
 
 #define KERNEL_ADDR             ((void *)0L)
 #define KERNEL_MAX_SIZE         ((long)_start)
+#define ARCH_COMMAND_LINE_SIZE  896              /* Taken from Linux kernel */
 
 char stack[PAGE_SIZE * 8] __attribute__((aligned(PAGE_SIZE)));
 IplParameterBlock iplb __attribute__((aligned(PAGE_SIZE)));
 static char cfgbuf[2048];
 
 static SubChannelId net_schid = { .one = 1 };
+static uint8_t mac[6];
 static uint64_t dest_timer;
 
 static uint64_t get_timer_ms(void)
@@ -158,7 +161,6 @@ static int tftp_load(filename_ip_t *fnip, void *buffer, int len)
 
 static int net_init(filename_ip_t *fn_ip)
 {
-    uint8_t mac[6];
     int rc;
 
     memset(fn_ip, 0, sizeof(filename_ip_t));
@@ -233,6 +235,66 @@ static void net_release(filename_ip_t *fn_ip)
 }
 
 /**
+ * Load a kernel with initrd (i.e. with the information that we've got from
+ * a pxelinux.cfg config file)
+ */
+static int load_kernel_with_initrd(filename_ip_t *fn_ip,
+                                   struct pl_cfg_entry *entry)
+{
+    int rc;
+
+    printf("Loading pxelinux.cfg entry '%s'\n", entry->label);
+
+    if (!entry->kernel) {
+        printf("Kernel entry is missing!\n");
+        return -1;
+    }
+
+    strncpy(fn_ip->filename, entry->kernel, sizeof(fn_ip->filename));
+    rc = tftp_load(fn_ip, KERNEL_ADDR, KERNEL_MAX_SIZE);
+    if (rc < 0) {
+        return rc;
+    }
+
+    if (entry->initrd) {
+        uint64_t iaddr = (rc + 0xfff) & ~0xfffUL;
+
+        strncpy(fn_ip->filename, entry->initrd, sizeof(fn_ip->filename));
+        rc = tftp_load(fn_ip, (void *)iaddr, KERNEL_MAX_SIZE - iaddr);
+        if (rc < 0) {
+            return rc;
+        }
+        /* Patch location and size: */
+        *(uint64_t *)0x10408 = iaddr;
+        *(uint64_t *)0x10410 = rc;
+        rc += iaddr;
+    }
+
+    if (entry->append) {
+        strncpy((char *)0x10480, entry->append, ARCH_COMMAND_LINE_SIZE);
+    }
+
+    return rc;
+}
+
+#define MAX_PXELINUX_ENTRIES 16
+
+static int net_try_pxelinux_cfg(filename_ip_t *fn_ip)
+{
+    struct pl_cfg_entry entries[MAX_PXELINUX_ENTRIES];
+    int num_ent, def_ent = 0;
+
+    num_ent = pxelinux_load_parse_cfg(fn_ip, mac, NULL, DEFAULT_TFTP_RETRIES,
+                                      cfgbuf, sizeof(cfgbuf),
+                                      entries, MAX_PXELINUX_ENTRIES, &def_ent);
+    if (num_ent > 0) {
+        return load_kernel_with_initrd(fn_ip, &entries[def_ent]);
+    }
+
+    return -1;
+}
+
+/**
  * Load via information from a .INS file (which can be found on CD-ROMs
  * for example)
  */
@@ -301,6 +363,18 @@ static int net_try_direct_tftp_load(filename_ip_t *fn_ip)
         if (!strncmp("* ", cfgbuf, 2)) {
             return handle_ins_cfg(fn_ip, cfgbuf, rc);
         }
+        if (!strncasecmp("default", cfgbuf, 7) || !strncmp("# ", cfgbuf, 2)) {
+            /* Looks like it is a pxelinux.cfg */
+            struct pl_cfg_entry entries[MAX_PXELINUX_ENTRIES];
+            int num_ent, def_ent = 0;
+
+            num_ent = pxelinux_parse_cfg(cfgbuf, sizeof(cfgbuf), entries,
+                                         MAX_PXELINUX_ENTRIES, &def_ent);
+            if (num_ent <= 0) {
+                return -1;
+            }
+            return load_kernel_with_initrd(fn_ip, &entries[def_ent]);
+        }
     }
 
     /* Move kernel to right location */
@@ -406,6 +480,9 @@ void main(void)
     if (fnlen > 0 && fn_ip.filename[fnlen - 1] != '/') {
         rc = net_try_direct_tftp_load(&fn_ip);
     }
+    if (rc <= 0) {
+        rc = net_try_pxelinux_cfg(&fn_ip);
+    }
 
     net_release(&fn_ip);
 
-- 
1.8.3.1